Synergex's page

Mutants and Masterminds did a good job of making D20 a classless system.

The largest problem I have expierienced with the magic item rules stems from Thier inception...
Way way WAAAAAAAYYY back in the time when Double G and Da Crew were creating this thing we all now like a great deal, they arbitrarily made up all of the original items. Names, stats, effects, all of it made up in random, arbitrary fashion. As the game grew and progressed, they and others made up new and different items as they felt was needed. But again this was done in an arbitrary, random fashion. These items were internally consistent in that there was no real "system" for thier creation and as long as the ones making the game liked it, it was "balanced". If you wanted your own items, it was up to your group to make them up on your own.

All this is fine if you are only ever gaming with your regular group, but as soon as you start mixing groups, which happened inevitably as the hobby's popularity grew, you ran into the problem of item x isn't good for group y. In order to address this, later designers attempted to standardize item creation by creating a system for making your own items. This was also fine, except that when the newer makers changed the magic items to match the new version of the game they made the same mistake the first designers did, they randomly assigned stats and abilities to the items arbitrarily, then made a system for creating your own items, instead of making the system, and then using that system to create the items.

This to me is how you fix magic items, make a good, balanced system for creating your own items, then use that system to create all of your "standard" items which will give you a great starting point for gamers that want to go out of those bounds to judge the relative power of thier custom items and will ensure that an item made at table x is power level and cost balanced for any standard game when following the system.

As a side note, spells have the exact same issues, and could be fixed the exact same way.

But this is just my 19 years of gaming talking.

As always: YMMV.